Orchards at Orenco: On Track to Become the Largest Passive House Project in North America

A
few months ago we had a two-part post about a sustainable building practice
referred to as Passive House (from the German passivhaus). The articles talked
about how stringent airtightness standards are positively impacting energy use
in these structures. We featured a new AMA project called Orchards at Orenco. Well,
the Passive House development has just gone through its first preliminary test and
returned an outstanding airtightness result of .075 ACH50!

This
recent test is an exciting result and a testament to how diligently the design
and construction teams are working to ensure an airtight structure. To put
things into perspective, the Passive House standard is .6 ACH50. The lowest
ACH50 on record is .05 for a tiny house in Alaska with one window and one door.
It’s incredible to think that this 57,000 sq. ft. building is returning results
comparable to a Passive House 20 times smaller.

The
test, part of achieving a Passive House standard, is known as a blower door
test. The measurement is generally displayed in ACH50, which stands for air
changes per hour at 50 Pascal. (A pascal is a unit for displaying pressure.)
The measurement is used to see how many times air would change in one hour.

To
better understand this measurement, picture a car tire. If that tire is
completely airtight, it can be filled with air, capped, and remain inflated
indefinitely. But what if the tire had a hole in it? To maintain inflation, air
would need to be continuously blown into the tire to replace the air leaking
through the hole. The larger the leak, the more air is needed. By measuring the
amount of air being blown into the tire to keep it fully inflated, we can
conclude how leaky the tire is.

The
blower door test does just that for buildings. It’s used to measure the amount
of air needed to keep a building at a pressure differential from inside to
outside of 50 Pascal. That measurement is used to quantify the amount of air
leakage and the effectiveness of any air sealing methods. This means that, if a
building is 4 ACH (Oregon’s requirement for new construction), then the air in
the building is completely changed four times in an hour. Older
homes—equivalent to “living in a barn”—are usually between 10 and 20 ACH50.

Construction
on Orchards at Orenco began earlier this year and is set to reach completion in
spring of 2015. When finished, this development will be the largest Passive
House project in North America. Although the .075 ACH50 number is not official,
this result reveals that the building is right on track to achieve its lofty
goals. Another test will be executed upon building completion, and the final
number will be an average of several measurements at different test pressures.

Both
Ankrom Moisan and Walsh Construction have worked painstakingly hard to achieve
this result. We are very excited to see how the project progresses. Stay tuned
for more results!